1. Field of the Invention
The present invention relates to satellite-based broadcasting systems. More particularly, it relates to systems for downlinking broadcast content data from satellites that are linked to ground-based uplink stations having remote beam-forming capability. Additionally, the present invention relates to coherent power combining techniques for downlinking various broadcast data streams over a common coverage area from multiple satellites that are linked to a ground-based uplink station.
2. Description of Related Art
Systems for broadcasting audio and video data from satellites in geostationary orbit (GEO), medium-Earth orbit (MEO), and low-Earth orbit (LEO) to ground-based users are well known in the art. Such systems generally rely on one or more ground-based uplink facilities to uplink content to the satellite. The satellite then downlinks the content to individual users in selected geographical areas. Some systems employ shaped reflectors to develop a downlink beam pattern to illuminate the selected region. Others employ multiple antennas or antennas with multiple elements in order to configure the footprint of the downlink beams.
However, nearly all of such systems are fixed at the time the satellite is launched and cannot be upgraded to keep pace with more advanced ground systems. Even those systems that maintain some satellite configurability must be controlled by complex systems on board the satellite and thus have inherently limited flexibility. Thus, it would be useful to provide a system with a radiation pattern that can be configured and controlled by ground-based uplink stations. In particular, it would be useful to provide a system that uses remote ground-based digital beam forming (DBF) systems to cause direct-broadcast satellites to radiate multiple downlink beams with configurable shapes pointing in configurable directions.